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November 24, 2017, 05:25:28 PM
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Author Topic: Too firm = worse handling?  (Read 518 times)

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Offline madlife

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Too firm = worse handling?
« on: June 16, 2017, 04:05:41 PM »
Who here has run a suspension that was too firm it made them feel "unsafe" on turns?

Having this problem with the MR2.  Syracuse roads are shit..  There have been times I was running an on ramp, or some very windy backroads,   I hit a hole/heave/bump and it lifted enough weight off the rear to shift the rear.  1-time the phenomenon induced snap-oversteer, but that was on a suspension with cut springs which I have since overhauled.

This doesn't happen often,  but its happened enough that is makes me nervous at times when I see a bump coming up.  Also in my growing older age,  I don't like the constant thud on the heaves every 50 years on the thruway.   Lastly,  the growing age of the car I seem to hear more and more rattles, and last year I rattled a grounding strap off the car.

I'm running Bilstein HD struts which universally I believe have more dampening.  How do you know if there is too much dampening,  or too stiff of a spring?   I'm hoping a soft spring will help.

FWIW... Tires are a 235/40/17 and 255/40/17 tire.   There is some sidewall on them.  I have RPF1s, so i'd hate to downsize to a 16.  Also 16" performance tire options are getting slimmer and slimmer.

Offline idipskoalmint

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Re: Too firm = worse handling?
« Reply #1 on: June 18, 2017, 10:45:51 PM »
Are the Bilsteins adjustable?
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Offline deadlydave

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Re: Too firm = worse handling?
« Reply #2 on: June 19, 2017, 08:05:07 AM »
Who here has run a suspension that was too firm it made them feel "unsafe" on turns?

The Baja's suspension was too stiff (as a whole)for most of the tires I was running on it.  It was probably too stiff in general, I had to run harnesses to stop my head from hitting the ceiling.  When your car is bouncing enough to unload the tires, it's a) slower and b) less safe.

Wagonzilla was the same thing once I went to coilovers.  Switching to a more serious summer tire helped a lot.  Sidewall flex and grip level worked with the suspension nicely.  My current coilovers are softer and actually have a progressive-rate spring in the rear which calms the back down some more.  The price for stepping up to big boy tires tends to be high: road noise, not the best wet performance, and expensive.

My IS300's suspension was too soft for the 225-45-17's I had on it, switching to 16's on mid-tier summer tires matched the suspension much better.  16" small-car-tire options, as you said, are dwindling.  Mine were the Dunlop Direzza DZ101's, the predecessor to the same tires I'm using on the Mazda (DZ102's).

My Legacy's suspension was too soft AND too low with KYB GR2's and Tien S-Techs.  Hitting the bump stops does effectively the same thing as having a way overdamped and oversprung coilover. going to WBM 2007, I hit a lane-wide pothole or mis-aligned expansion joint, got a bone-jarring slam through the whole car.  It then launched off the bump stops, and skittered across the road 8 or 10 inches towards a jersey barrier.  Pucker Factor: 5/5 do not want.

If you go to a softer spring, try and do a little homework and get a spring that sits taller.  You've got a lightish, short wheelbase, Mid Engine/Rear Drive car, sort of designed to 'rotate'.  You could also try your hand at doing "DIY" coilovers using your Bilsteins with Ground Control Coilover Sleeves and springs spec'd to a rate and height of your choosing.  A lot of semi-budget autocrossers do this...it would allow you to get a somewhat taller spring that was also softer.  A lot of cars that are popular for auto-x also have spring perch options that make the perch itself smaller giving you more  room for shock travel.

Offline idipskoalmint

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Re: Too firm = worse handling?
« Reply #3 on: June 19, 2017, 08:17:10 PM »
Know how I know it's just a bunch of dudes on this forum? There's talk about being "too stiff"...

#thatsNOTwhatshesaid

My current coilovers are softer and actually have a progressive-rate spring in the rear which calms the back down some more.  The price for stepping up to big boy tires tends to be high: road noise, not the best wet performance, and expensive.

The price for those coilovers wasn't too bad though :D
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Offline BenjiJosef

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Re: Too firm = worse handling?
« Reply #4 on: June 20, 2017, 09:06:11 AM »
Know how I know it's just a bunch of dudes on this forum? There's talk about being "too stiff"...

#thatsNOTwhatshesaid

The price for those coilovers wasn't too bad though :D
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Offline madlife

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Re: Too firm = worse handling?
« Reply #5 on: June 20, 2017, 02:07:16 PM »
Are the Bilsteins adjustable?

Nah they aren't...

Offline Kavik

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Re: Too firm = worse handling?
« Reply #6 on: June 20, 2017, 10:18:45 PM »
Maybe a dumb question....but how about the rsb?
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Offline stylesrex

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Re: Too firm = worse handling?
« Reply #7 on: June 21, 2017, 11:58:03 AM »
A dampers job is to controll oscilations of the vehicle.  A miss match of spring and damper can lead to undesirable characteristics like harshness

To really understand whats going on with your car.  Id look at curb weight, weight distribution, stock spring ratres.  Then calculate motion ratios and wheel rate frequencies.  Then you can re do the calculations with your current spring rates and analyse results

let me know if you want help

Offline madlife

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Re: Too firm = worse handling?
« Reply #8 on: June 21, 2017, 03:59:27 PM »
A dampers job is to controll oscilations of the vehicle.  A miss match of spring and damper can lead to undesirable characteristics like harshness

To really understand whats going on with your car.  Id look at curb weight, weight distribution, stock spring ratres.  Then calculate motion ratios and wheel rate frequencies.  Then you can re do the calculations with your current spring rates and analyse results

let me know if you want help

That sounds pretty greek to me! I didn't know you can mathematically determine this.    let me dig up the info on this and I'll post it up tonight.

Offline madlife

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Re: Too firm = worse handling?
« Reply #9 on: June 21, 2017, 04:32:39 PM »
TRD Springs  {Current}
Aprox. 1" lower riding height {Than the 93 springs}
Front spring rate 168 lb/in
Rear spring rate 308 lb/in

Stock {My car is a 92, but a ton of suspension bits have been swapped over to the 93+.  There were a bunch of changes to help reduce "Snap oversteer"}
1991 Turbo
F: 130lb/in. linear
R: 209lb/in. linear

1993 (don't know whether NA or Turbo, is there a difference?)
F: 130lb/in. linear
R: 210lb/in. linear


Reference:  with some other spring rates for reference = http://www.mr2oc.com/61-3sgte-turbo/191464-stock-spring-rates.html#post1977902

_____________________________________________________________________

Weight lets just say is 2750 given my cars "mutt" status.
43%F  57%R

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Offline BlackParis

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Re: Too firm = worse handling?
« Reply #10 on: June 21, 2017, 09:26:34 PM »
Bilstien HD are intended and valued for stock height,
Bilstien sports are intended for slight lowering (not in excess of 2 inches in most applications)

Your Fronts are struts... ? What are your rears? Trailing arms? I believe?

I know mr2 rear koni inserts are a shorter stroke replacement on my front strut inserts on the Supra.

So inversely, if you wanted a little more rear travel  to help compensate for bumps, you could put the mk2 Supra inserts inside your mr2 cases with a little lengthening. This would help keep you off the bump stops, which is most likely your problem. You are probably much too soft for being lowered. 168/222 would be an evenly balanced wheel rate for the weight of your car. So depending where on the control/trailing arm your spring mounts, that what determines your effective wheel rates. The rear if trailing arm, could very easily be at a ~70% effective rate and that's why such a higher rate is required.

my recommendations.

removing more bumpstop, and perhaps trying different dampners (konis sports/yellows)

or just getting rid of all of it and going for a full adjustable coilover something in the 350-300 wheel rate range.. and getting the car corner weighted

FYI 2600lb rally cars on dirt typically aim for a 200ish wheel rate which is about where you are at... so you certainly aren't too stiff...
« Last Edit: June 21, 2017, 09:45:39 PM by BlackParis »
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Offline madlife

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Re: Too firm = worse handling?
« Reply #11 on: July 17, 2017, 10:57:52 AM »
Bump this up..

I forgot to think about the tires!!   late last summer I had Direzza Z1 tires installed.    The Ultraleggras I got for my OBXT have the same tire,  same profile, {slightly narrower}.  Holy heck the small frost heaves are very noticeable in the OBXT now.   Doesn't slam like the MR2,  but the OBXT is on Tein basis coilovers {very comfy}.

I had 225/50/17 Nokian snow tires on the OBXT
now 235/40/18  Direzza Z1
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